On Dactylocahjx pumiceus {Stutchhury). By W.J.SolJas. 131 



into interior tubes. In Coeloptychium, however, all these features 

 possess a regularity which is not to be found in dactylocalyx ; the 

 ridges in the former sponge are more uniform in size, straighter in 

 direction, and more regular in their bifurcation and anastomosis ; 

 the circular openings upon them are also of very uniform diameter, 

 and are arranged at equal distances apart in regular rows. 



Notwithstanding tliese difi'erences of detail, however, an obvious 

 general resemblance exists between the two sponges when their 

 lower surfaces are alone compared, while, as regards general exter- 

 nal form, one must allow that Dactylocalyx, especially the variety 

 I). Stutchburyi, represents in a striking manner some of the widely 

 infundibuliform specimens of Coeloptychium. In other respects 

 more essential difi'erences are to be found. 



The character of the nodes in the newly formed network of 

 Dactylocalyx may be also alluded to again, since they are always 

 hollow and reticulate to begin with, and not solid throughout as 

 in the later stages of growth ; moreover, as already stated, the 

 young node often exhibits an octahedral arrangement in its reticu- 

 lation, which clearly resembles that of the true hollow-jointed 

 Hexactinellids, and thus passes through a stage which in the latter 

 sponges has become persistent. From this it would appear that in 

 the ancestral form of Vitreo-hexactinellid the nodes were all cha- 

 racterized by a lanteru-like arrangement, and that while in some 

 of its descendants the subsequent deposition of silica at the node 

 took place chiefly along the octahedral fibres, and thus gave the 

 Yentriculite knot, in others it followed no definite direction, but 

 simply filling up the interspaces, produced the solid node of such 

 forms as Dactylocalyx. 



Dactylocalyx pumiceus, var. Stutchhiryi (Plates V. and VI.) — 

 This form will not require any lengthy description, since it agrees 

 in all important characters with the preceding, and it is only in 

 details of quite trifling value that any difierence exists. The general 

 form is that of a vase or flower-basket, but with a much less ex- 

 panded brim than the type of D. piomiceus ; its walls are also a 

 trifle thicker than the latter, and the ridges and grooves on its 

 inferior surface are deeper, narrower, and straighter. The elliptical 

 margin of the cup measures 1 foot 1 ^ inch along the major axis, 

 and 10 inches along the minor axis. It is 5 inches in height. The 

 surface of attachment, i. e. the base of the pedicel is covered with a 

 layer of denser tissue than occurs elsewhere in the sponge. The 

 fibres of this layer are usually flattened, smooth, seldom tuberculated, 

 and only at intervals connected with the interior body network. 

 Between such points of connection the layer often remains single in 

 thickness, and being flattened and smooth on both faces, presents 

 the appearance of a cribriform plate (Plate VIII., Fig. 4). Some- 

 times the rounded holes of this plate are filled in with a delicate 



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